This invention relates to a cannulated orthopedic screw having particular application in the distal proximal fixation of lateral malleolus fractures. The ankle joint is made up of three bones coming together. The tibia, which is the main bone of the lower leg, makes up the medial or inside anklebone. The fibula is a smaller bone that parallels the tibia in the lower leg and makes up the lateral or outside anklebone. The distal ends of both the tibia and fibula are known as the malleoli (singular is malleolus). Together, they form an arch that sits on top of the talus, one of the bones in the foot. These three bones (tibia, fibula, and talus) make up the bony elements of the ankle joint. A fibrous membrane called the joint capsule, lined with a smoother layer called the synovium, encases the joint architecture. The joint capsule contains the synovial fluid produced by the synovium. The synovial fluid allows for smooth movement of the joint surfaces. The ankle joint is stabilized by several ligaments, which are fibers that hold these bones in place.
Ankle fractures occur when the malleoli are broken. These fractures are very common. Ankle fractures can happen after falls, car accidents or twisting of the ankle. One, two or all three malleoli can be broken.
Fixation of a lateral malleolus fracture has evolved over many years. Initial treatment was a closed reduction with a cast or splint. Later practices included the use of rush rods, screws and simple plates. More recent treatments have included the use of stronger and wider plates with screws or locking plates.
Patients are instructed in non-weight bearing or minimal weight bearing activities based on the fracture pattern, bone density, weight of the patient, mental condition and level of fixation obtained at surgery. Good accurate fixation in young patients is essential for good long-term results but even with accurate fixation, some patients develop non-union or articular cartilage damage and require some type of replacement later due to the cartilage damage or infection.
Older patients with osteopenia and more physical problems present a different problem. Most fixations of the lateral malleolus if displaced require open striping of tissue from the distal fibula and plate fixation with multiple cortical and cancellous screws. A distal to proximal fixation of the lateral malleolus offers another way to reduce and stabilize the lateral malleolus. Such a procedure would alleviate the need for open fixation with plates and screws especially in older patients with Alzheimer's, osteoporosis, and other medical conditions. This would permit a quicker fixation with a retrograde screw from the distal tip of the lateral malleolus up the canal of the proximal fibula. At present, there is no screw available that permits larger distal fixation and smaller proximal fixation.